The invention relates to non-explosive, frangible actuator devices for quickly releasing loads.
Non-explosive frangible actuators are used to perform a task, often releasing a tensile load (such as a stowed solar array or antennae on a satellite) upon electronic command. Because of the damage of explosion in aerospace applications, and the weight of the satellite and other loads to be released, actuators must first restrain and then quickly release tremendous loads with a minimum mechanical shock imparted to the surrounding separate components or devices. Typically, such actuators will utilize a multi-part spool held together by a wound restraining wire (with memory). A load is restrained by the barrier formed by the intersection of the parts of the spool (when held together by the restraining wire). A pin is provided which bares against the spool at one end of the pin and holding the load at the other end of the pin. A small frangible fuse keeps the restraining wire from unraveling until a weak electrical current causes the frangible fuse to fail in tension, allowing the restraining wire to unwind and thus freeing the parts of the spool to separate, eliminating the resistance to the load. Some actuators apply the full force of the load to the spool, while others utilize a series of moving parts to create a mechanical advantage, so that only a small portion of the load need be resisted by the spool. Typically prior art devices used a single power supply. As detailed below, prior art devices have exhibited a number of problems.
In many applications, such as aerospace, the device must function properly the first time, and at a precise, predetermined time. The lack of a redundant power supply and electrical wiring can cause the device to fail or not operate successfully.
Prior art devices have also employed plastic actuators. In the past, metal actuators were thought to be impractical because the power to the fuse wire could short or ground on the entire device, causing the fuse wire not to actuate and perform the required function. Such devices are limited in the load that can be directly restrained by the actuator spool by the tensile strength of the plastic. One prior art device by G and H Technology (xe2x80x9cG and H 8024xe2x80x9d) attaches an insulator on the fuse wire, which unfortunately becomes debris after actuation. The G and H 8024 also utilizes a ceramic actuator, made of aluminum oxide ( Al2O3) to make their device as non-conductive as possible. Just as with plastic actuator spools, aluminum oxide lacks the tensile strength of steel.
Prior art xe2x80x9cmechanical advantage devicesxe2x80x9d have an additional problem. In such devices, the load is released almost instantaneously, risking high mechanical shock output. Although xe2x80x9cmechanical advantagexe2x80x9d actuators have a series of events that precede release (e.g., fuse failure causing spool separation resulting in a series of parts moving and releasing other parts), the actual release of the load is quite sudden.
Prior art devices can only be loaded from one side (i.e., the load can either be pulling on one side or pushing against the other direction). Thus separately designed actuators must be employed for different applications.
Additionally, prior art units, such G and H model no. 8024, use a conical (or funnel) shape for the top of a release pin. As discussed within, this allows no tolerance for misalignment.
What is needed is a frangible actuator that uses a direct release mechanism, has a redundant power supply, allows use of a metal spool release without grounding the fuse, and avoids failure due to excessive friction during release.
In a first embodiment, the present invention provides a redundant power supply for an actuator with two actuator terminals, which block and then release a load responsive to current from the power supply, which includes at least two power supplies, each connected to the actuator in parallel whereby should one fail upon activation, the other will still actuate the device.
In a second embodiment, the present invention provides a frangible actuator comprising an actuation barrier with a plurality of restraining parts, having a blocked position and an open position; a frangible restraint for maintaining and releasing said plurality of parts from the blocked position, the frangible restraint failing in tension upon the application of an electrical current; a restraining wire having a secured position and a release position, for holding and releasing the plurality of parts; an insulator hub made of a nonconductive material surrounding a loop end of the restraining wire, with the frangible restraint passing over and holding the restraining wire in the secured position and allowing said restraining wire to move into said release position when said frangible restraint fails in tension in response to the application of electrical current.
In a third embodiment, the present invention also provides an actuation barrier comprising a plurality of restraining parts with a blocked and open position and an interior surface; an activation pin having a head portion and a load portion interconnected to a load to be released adjacent to the load position and bearing against the restraining parts at said head portion when the restraining parts are in the blocked position and passing beyond the restraining parts in said open position; and the interior surfaces have at least one depression section against which the head portion of the activation pin does not bear when the restraining parts are in their blocked position.
In a fourth embodiment, the present invention also provides a base portion and restraining parts made primarily of steel at least partially coated with aluminum oxide.
In a fifth embodiment, the present invention also provides at least one and ideally two restraining pins, pin rigidly connected to the base portion and bearing against at least one of the plurality of restraining parts when the actuation barrier is in a blocked position, restraining movement of the actuation barrier relative to the base portion when the barrier is in the blocked position.
In a sixth embodiment, the present invention also provides a restraining wire wound around the actuation barrier at least once when in the blocked position to hold the restraining parts together, and unwinding to release the parts to move the barrier into the open position, and the diameter of said actuation barrier is equal to 0.8 times the square product of the diameter of the wire divided by a constant in the range of 0.021 to 0.031 and ideally 0.026.
In a seventh embodiment, the present invention also provides a head portion with two parallel flat sides and at least one restraining channel, located between the restraining parts, each restraining channel having a lower end and an upper end, said restraining channel restraining rotational movement of said head portion as the head portion passes through the channel but allowing rotational movement as the head portion passes above the channel so that the head portion may be inserted into the actuator and received by the lower end of the restraining channel with or without a load attached, passed through the channel and above the upper end thereof, rotated, ninety degrees, lowered and allowed to bare against and be resisted by said actuation barrier.